Density metrologists standardise on Watson-Marlow 400M OEM pumps

H&D FitzgeraldH&D Fitzgerald, the world's leading laboratory in the field of density metrology is benefiting from the advantages offered by 400M OEM peristaltic pumps from Watson-Marlow Fluid Technology Group. For the past 10 years, H&D Fitzgerald Ltd. has been using the pumps in its automated density gradient column fillers, which are now in active service in laboratories around the world. Watson-Marlow’s decade-long relationship with the company demonstrates its ability to forge long-term strategic supply relationships through a highly reliable product offering.

H&D Fitzgerald Ltd is recognised as a world authority on density measurement and calibration. Their facility in North Wales is purpose designed, built and equipped specifically for density metrology, and is the only such laboratory of its kind in the world. The company holds both ISO 9001 and ISO 17025 accreditation, guaranteeing the highest standards of quality and technical capability.

Around 10 years ago, the company brought a landmark new product to market – the Density Gradient Column Filler. The instrument provides a ground-breaking automated approach for laboratories measuring the density of solid samples, and replaces the previous 'manual' method which was both time consuming and required a highly skilled technician.

No more manual filling

"Manually filling a gradient column typically involves the use of two flasks featuring valves and stop-cocks," explains Will Webster, Commercial and Marketing Manager at H&D Fitzgerald. "This was a slow, laborious process requiring considerable skill on the part of the technician, and what's more, the resultant gradients were not always reliable. In contrast, our instrument is completely automated, thus eliminating the skill requirement and ensuring total process repeatability. In addition, the entire process only takes around 60 minutes."

The company's microprocessor-controlled density gradient column filler mixes two miscible liquids of different density, in constantly variable proportions, which is where two Watson-Marlow 400M OEM pumps are deployed.

"We required pumps that were compact, cost-effective and offered the capability to pump at low flow rates to ensure no bubbles were introduced to the process," says Mr Webster. "The level of controllability offered by the Watson-Marlow 400M was a prime purchase decision as it helps ensure the quality of the column."

Once filled, calibration is achieved by dropping solid objects of known density into the column and measuring the height at which they come to rest. The relationship between height and density allows users to measure items of unknown density that are subsequently dropped into the column.

Used around the world

"We have sold units to labs all around the world – China, USA, Dubai to name a few," says Mr Webster. "The majority of users are in the plastics industry, where manufacturers need to ensure that plastic granules used in the extrusion or moulding process, meet their density specification. Further customers include those in the composites, nuclear, biological and specialist agriculture industries, as well various research laboratories and universities."

A wide range of liquids can be used to make density gradient columns. These may include alcohols, water, aqueous salt solutions, and brominated solutions. Chemically aggressive liquids can be handled by the Watson-Marlow 400M  single-channel pump, as the moving parts do not come into contact with the liquids being pumped, and the pump can be fitted with chemical resistant tube elements. This is in stark contrast to alternative types of pump technology.

Cost effective solution

The 400M is a compact pump designed with the shaft supported by ball bearings for long service life. It uses tubing available in four sizes and is stackable to four channels (200 ml/min per channel). It has been designed as an OEM pump offering premium features at an economical price.

Importantly for H&D Fitzgerald, the pump offers simple tube loading and luer fittings for easy connection to transfer tubes. The tubes are completely enclosed in the pumping chamber.

Ultimately, the automated density gradient columns fitted with Watson-Marlow OEM pump technology are helping users to achieve fast, accurate and consistent building of density gradient columns. Furthermore, fully automated filling leaves the technician free to undertake other tasks and duties.

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